Methylchloroform is subject to degradation and forms corrosive products in the presence of certain metals, especially aluminum, zinc, iron, copper and their alloys. Most stabilized methylchloroform compositions contain a combination of compounds as the stabilizer, some of which are intended to stabilize either the vapor or liquid and others which will be effective in both. The particular ones required will depend upon the use for which the methylchloroform is intended. This solvent is useful in cold cleaning, hot cleaning and in vapor degreasing. Since the introduction into the marketplace in 1957-1958 as a commodity the largest volume of 1,1,1-trichloroethane sold throughout the world contained 1,4-dioxane, nitromethane and 1,2-butylene oxide as the sole inhibitors. The next largest volume has been that containing 1,3-dioxolane (a five-membered dioxygen heterocycle, a compound very similar to 1,4-dioxane), nitromethane, 1,2-butylene oxide and in most instances one or more materials (such as lower ketones and/or alcohols) which account for the remainder of the ten principal compounds used in industry to stabilize 1,1,1-trichloroethane. To illustrate the wide variety of stabilizers used in combination with the nitroalkanes, numerous patents may be cited. In U.S. Pat. No. 2,970,113 an acetylenic alcohol and dioxane are employed with nitroalkanes; U.S. Pat. No. 3,049,571 employs sec-butyl alcohol, an alkynol, dioxane and butylene oxide in addition to the nitroalkanes. U.S. Pat. Nos. 3,518,202 and 3,549,715 both employ acetylenic alcohols along with nitroalkanes and auxilliary stabilizer components. Other patents employ esters (U.S. Pat. No. 3,060,125); esters and dioxane (U.S. Pat. No. 3,113,155); tert-butyl alcohol, butylene oxide and ethers (U.S. Pat. No. 3,281,480); and amines, butylene oxide and dioxane (U.S. Pat. No. 3,629,128). Even more recently issued patents employ dioxane, t-amyl alcohol and butylene oxide in combination with a nitroalkane (U.S. Pat. No. 4,115,461) and the combination of glycidol, dioxane and butylene oxide (U.S. Pat. No. 4,152,359).
U.S. Pat. No. 3,974,230 employs either a mixture of methyl butynol and t-amyl alcohol or methyl butynol alone or along with nitroalkanes and alkylene oxides as the stabilizing component.
In the light of recent attacks by environmentalists on some of the chlorinated hydrocarbons, allegedly due to their environmental hazards, as well as controls concerning their use resulting from the Occupational Safety and Health Act, it becomes necessary for the manufacturers of 1,1,1-trichloroethane to provide this safer solvent, from an environmental, safety and health standpoint, with inhibitor systems which will be in comformance with environmental standards.
It is the object of the present invention to provide an industrially useful combination of stabilizers for 1,1,1-trichloroethane which will inhibit, even under the severe stress of vapor degreasing, the 1,1,1-trichloroethane-aluminum reaction as well as the reactions attributable to the presence of zinc, copper and iron, their alloys, and water.
The inhibitors employed to stabilize methyl chloroform against aluminum and zinc, i.e. dioxane and butylene oxide are not very effective for any appreciable length of time in the absence of a nitroalkane.
The present invention employs a stabilizer for methylchloroform in which the nitroalkane is replaced with an alkynol. In this stabilizer combination no nitroalkane is required.